Air and water supply system for dental units



Feb. 16, 1960 E. R. ZIEGLER ETAL 2,924,880

AIR AND WATER SUPPLY SYSTEM FOR DENTAL UNITS 3 Sheets-Sheet 1 Filed March 14, 1956 INVENTORY. ME! R ZIEGLER,

III-FRED ll CRAFT y NORMAN E. art/mm I AND M DDUGL "085$ ATTDHNEY Feb. 16, 1960 E. R. Z IEGLER ET AL 2,

AIR AND WATER SUPPLY SYSTEM FOR DENTAL UNITS Filed March 14, 1956 3 Sheets-Sheet 2- 1 lllllll l l 'w 9 1/////////A (((\(\\\,v

IN V EN TORS. was: a. ZIEGLER, name-a II. man;

y NORMAN s. LAUTERBACII .4110 m oouaus 065$ A ORNEY Feb. 16, 19 0 E. R. ZIEGLER ET AL I 2,924,880

AIR AND WATER SUPPLY SYSTEM FOR DENTAL UNITS Fi led March 14, 1956 3 Sheets-Sheet 3 INVENTORS'. EUGENE R. ZIEGLER, MILFRED fl- 6R4! 1; BY NORMAN E LAUTERBACH MID W DOUGLAS 0BE$ urranusr United States Patent AIR AND WATER SUPPLY SYSTEM FOR DENTAL UNITS Eugene Russell Ziegler, Spencerport, Milfred H. Craft, Rochester, Norman Edward Lauterbach, Pittsford, and William Douglas Nobes, Rochester, N.Y., assignors to Ritter Company, Inc., Rochester, N.Y., a corporation of Delaware Application March 14, 1956, Serial No. 571,565 9 Claims. case-2s field have been advocating higher drilling or cutting speed for many years. Higher cutting speeds, however, produce greater heat during the drilling or cutting operation and require some method of dissipating the heat thus generated. Higher drilling speeds have led to the development of various systems for supplying a coolant to the cutting tool. In some systems air only is supplied to the cutting tool; in other systems only water; and in still other systems air or water or a mixture of air and water may be supplied to the cutting tool.

These latter systems, that is, those which enable the dentist to select the coolant medium most suitable for the operating being carried out have comparatively recently come to the fore because of their versatility not only because various dentists have preferences in the type of coolant to be employed but also because a particular operation being performed may require for best operating conditions air alone, water alone or an airwater spray. For example, in some operations the major problem of the dentist may be the rapid removal from the drilling area of tooth debris, amalgam chips, blood, saliva and pumice. Under such conditions a water stream which will rapidly wash away the debris would probably be the most desirable form of coolant. In fact, some dentists are now working with a vacuum producing apparatus which will pull water and debris away from the tooth as rapidly as the water is supplied thereto and the debris accumulates. In other operations, the dentist may wish to maintain the tooth in a substantially .dry condition during the operation, while at the same time removing debris from the drilling area. Under such conditions an air stream alone may be the most desirable coolant. Aside from special considerations which make either air or water the most desirable form of coolant, for general purposes, most dentists appear to prefer an air-water stream and more particularly an airwater spray.

One of the important considerations is the versatility of the system. That is the ability to switch rapidly from one form of coolant to another. For example, the dentist may be using an air-water spray which may cause fogging of the mirror used by the dentist to provide visibility of the work being performed. Under such conditions the dentist may wish to switch rapidly from the air-water spray to air alone to dry the mirror surface while the operation is in progress.

The above considerations have led to many problems which insofar as we are aware have not been fully solved. Among these problems might be mentioned that the versatility of the system must be accompanied by means enabling the selection of the type of coolant desired with a minimum t sfiet 0 1 the P rt of he n is The switch 2,924,880 Patented Feb. 16, 1960 from one coolant to another must be accomplished rapidly and with almost no conscious efiort on the part of the dentist. Another problem lies. in securing a proper air-water spray so that the spray is supplied to the cutting tool in almost a mist. The solution of this problem requires accurate control of the volume and pressure of water supplied to the hand piece. Moreover, it requires proper mixing of the two streams at or adjacent the cutting tool. Still another problem encountered is the prevention of water drip from the hand piece when its use is discontinued and without the necessity of employing shut off valves on the hand piece. Shut off valves on the hand piece not only make the hand piece more bulky and cumbersome to use but also such valves frequently fail or become damaged in use.

An object of the invention is to provide a versatile coolant system for the cutting tool of a dental unit wherein the dentist may selectively control the supply of an air stream, a water stream or an air-water spray to the cutting tool and the area being operated upon.

Another object of the invention is to provide a versatile system wherein valves on the hand piece are eliminated; wherein selection of the type of coolant desired may be accomplished quickly and conveniently; and wherein, after selection, the desired coolant is supplied automatically when the dental engine is started.

Another object of our invention is to provide a versatile system for supplying coolant to the cutting tool of the dental engine which enables the use of municipal water supply for the water coolant. as distinguished from a water reservoir which must be replenished at frequent intervals.

Another object of our invention is to provide a versatile system for supplying air, water or a mixture of air and water to the hand piece wherein quickly detachable means are provided for attachment to the conduits which bring the air and water to a position adjacent the hand piece enabling the dentist to change rapidly from a straight hand piece to a contra angle hand piece or vice versa.

A further and one of the most important objects of our invention lies in a pressure-volume control system for the water supply to enable the supply of water to the hand piece in a thin stream or almost in droplets in order to produce a finely divided air-water spray or almost a mist of air and water.

Another object of our invention lies in directing the air and water streams at an angle to each other with the water being supplied in a thin stream or almost droplets wherebythe air stream breaks up the water stream just prior to or at the drill to the end that a finely divided air-water spray is supplied which encompasses not only the drill but also the area being operated upon to the end that the drill and the area being operated upon are cooled and debris is removed from the cutting area with a minimum amount of water being supplied to thereby minimize the use of a saliva ejector and reduce interruption of the dentist in his work by reason of accumulation of liquid in the patients mouth.

More specifically our invention contemplates the provision of a versatile coalant system in which the air, water or air-water spray are positively controlled by shut off valves; the supply of water is metered and so controlled as to substantially eliminate dripping of water at the hand piece when use of the system is discontinued without the use of shut ofi valves on the hand piece.

Other objects and advantages of our invention will be clear from the following description, when taken in connection with the accompanying drawings, in which:

Fig. 1 is a view partly in section showing the dental arm, its jointed appendages, the hand piece and drill, the dental engine and the air and water conduits forcou.

ducting coalant to thehan'd piece, the view also including a diagrammatic "showing of the -system for controlling selectively the supply of air, the supply of water or the supply and air-water spray .to the hand piece;

Fig.2 is a side elevation, partly in section, showing a contra angle hand piece, showing the discharge end of one of the coolant conduits and'illustrating how, when anair-water spray .is desired, the air breaks up the water into a finely divided spray or mist which envelopes the cutting element and the area being operated upon;

Fig. 3 is a bottom view of Fig.2 illustrating the angular relationship of discharge of the air and water streams so that when the'water is supplied in a thin, metered pressure controlled .stream, almost in the form of a drizzle, the air will pick up the water, breakup the streamand supply a finelydivided air-water spray;

Fig. 4 is a view similarto Fig. 2 showingthe coolant supply system of our invention in .use with a straightdrill;

l ig. 5 is aplan view o'fFig. 4;

Fig. .-6 is a perspective-view showing the detachable connection between the air and water conduits-from the dentalunit and the conduits partly carried by thehand piece; and

'Fig. 7 .is aperspective view similar to Fig. 6 showing the hand piece conduits disconnected from the dental unit conduits.

.In Fig. :1 we have shown one form'of dentaldrilling unitin which ourcoolant supplytsystem'may be embodied. It will be understood, however, that this is merely for purposes of illustration and that the system of'our invention may be embodied in other types of drilling units. The particular dental drilling unit shown comprises an equipmentstand only partly shown and generally indicated by the numeral 11, a dental engine 12 which may be enclosed by a readily removable hood or cover 13, a dental arm, generally indicated by the numeral Y14, and pivotmeans generally indicated by the numerals 16 and 17'by-which the dental arm may be swung in a horizontal plane and a vertical plane.

Depending from the outboardendof the dental arm are appendages, generally indicated by the numeral 18, which include articulated members which'carry the pulleys for the drive belt 19 for rotating the pulley 21 carried by the hand piece generally indicated by the numeral 22.

Water is supplied to the hand .piece from aiconnection 23 and air from a connection 24. Water is supplied from the connection 23 to a'water conduit 26and air from the connection v24 to an air conduit 27. The conduits 26 and 27 are for the mostpart of flexible, plastic'materials and extend through the dental arm 14 around the articulated 'joint, generally indicated by the numeral 28 and as illustrated at 29, through the arm 31, around the articulated joint 32, asillustrated at 33, through the articulated "arm 34 to a connecting block 36 carried 'by 'a "support "arm 35. .At the connecting or mounting block 36, the air and *water conduits are'connected to :a detachable air and water conduit partly carried by the hand piece and generally-indicated by the numeral 37. 'The detachable hand piece conduits and their support 'will be described in more detail later. Forourpresent purposes all'thatis essentialis an understanding that water and air are supplied respectively from the connections '23-a'nd24 to the mounting block 36.

In Fig. 1 we have diagrammatically illustrated the system for controlling the supply of air "and water respectively to the connections 23 and '24. .First considering the air supply the dotted line 41 illustrates an air line connected to .a source of air under pressure illustrated at 42. Such air supply systems are usually available in a dental office'and include an 'air'compressor 'and a storage tank together with means for controlling the pressure of air carried in'the tank. The airline extends to a solenoid valve '43 which may be of conventional construction. When the solen'oidvalve is open'theai'r .flows'tthrough'aa :line 44 through :a "hand control valve 46 to the air connection 24. The hand air control valve 46 maybe placed at any convenient point in the line from the source of air under pressure and is preferably located so that the dentist has access to it. Adjustment of this valve need be made only infrequently, if at all, since once it has been set for a particular air pressure and assuming the pressure of air from the source is substantially a constantyit isseldom necessary to adjust the .air ,pressure.

The Water supply has been indicated by the numeral 47 which .is a connection to the municipal water supply. From the municipal water supply the Water flows to heating unit or tank 48. One of the important'aspects of our invention lies in the fact that the control system employed, as will presently appear, enables the use of solenoid valve 53 similar to the solenoid valve 43, a

line 54, a metering valve 56, a .line 57, a hand control valve 58 to the water connection 23.

The pressure regulator may be of conventional construction and includes the usual hand operated control by which the regulator pressure-may be set. The meter ing valve 56-may take the form of a needle valve which may be hand regulated tocontrol the volume of flow to the Water connection 23. The hand-control valve 58 may may be placed in any location convenient to the dentist. It will be understood that all of the elements previously enumerated are located and housed within or on the 7 dental stand, generally indicated by the numeral 11.

A-rnotor controller, generally indicated by the numeral 61, has been illustrated only diagrammatically but it will be understood that it includes suitable foot actuated controls .62, a resistance 63, a contact arm 64 adapted to sweep over theresistance 63 upon actuation of the foot controls 62,'a line connection 64 and a segment 66 to which electrical conduit 67 is connected. The operation of foot'controllers for dental units is well understood in the art and further description .of them is unnecessary.

The conductor 67 is connected through a lead 68 to a switch 69'and through a lead 71 to a switch 72. The other side of the switch 69 is connected through a lead 73 to the solenoid valve 53 While the otherside of the switch 72 .is connected through a lead 714 to the solenoid 43. The motor 12 is connected througha lead 75 to the foot controller'61, the other'sideof the motor being connected through a lead 76 tothe line. The lead 76connects with the solenoids -43tand 53.

It will now be apparent that'with both switches 69 and 72 in the olf position upon actuation of the foot controller to start the motor 12 neither air or water are supplied to the ..hand'piece. vThisjs desirable under certain conditions of'operation particularly when the drill is to operateat lowspeed. With the water switch 69 on, when the foot controller is operated to start the motor,-the solenoid valve 53 is opened to supply Water through the metering "valve to the hand piece. When both the water switch 69 and the air switch 72 are on. both solenoid valves 43 and .53-are actuated and a mixture of air and water are supplied :to .the hand piece when the foot controller :is actuated to start the motor 12. When the water switch 69 is in the off position and-the air switch 72 "is in the on position, only the solenoid valve 43 is operated when the foot controller Gris actu- =ated=and onlyairisstrpplied to the'handfpiece.

One of the problems encountered in supplying coolant fluids. to the hand piece is the proper control of the flow through the air and water conduits. In the past control of flow through the conduits has, for the most part'been by means of valves located on the hand piece. Usually these valves have been of the type requiring pinching, pressing or otherwise deforming flexible conduits. The use of valves on the hand piece make the hand piece more bulky thereby interfering with the convenient use thereof by the dentistf Moreover, repeated pinching of the flexible tubing causes wear and frequently results in rupture-of the'tubing. In addition such valves arenot always positive in their action and may fail to close fully against leakage. In our system as previously described we employ solenoid actuated valves which may be located in the dental unit and are rapid and positive in their action. The controls for the solenoid actuated valves may be located in any convenient position within easy reach of the dentist. One convenient position for the control switches 69 and 72 is on the dental arm. By using control switches for the solenoid actuated valves conveniently located for use by the dentist and placing these control switches in circuit with the foot controller, reliance on valves such as those which pinch flexible tubes or depend upon manual .operation is eliminated.

' A further problem encountered in supplying water to thehand piece is adequate control of the pressure and volume of water supplied. In many of the systems heretofore employed, a separate supply tank requiring frequent filling was used primarily because of the problem encountered in connecting up such systems to a municipal water supply. It will be appreciated that the pressure of municipal water supply systems varies from approximately 30 lbs. to 50 lbs. and greater variations are not uncommon. We have found however that if the pressure is maintained at from 5 to lbs. this degree of fluctuation at the lowered pressure provides adequate pressures forthe dentists use without causing faulty operation due to :excessive pressures. Accordingly we provide a pressure regulator 51 which is arranged to step down the pressure normally available in municipal supply systems to approximately 5 to 10 lbs. the exact pressure drop depending upon the pressure in the municipal water supply. The pressure regulator 51 may be of any conventional construction and since such pressure regulators are well known in the art, its construction need not be described.

A further problem in connection with a system for supplying water to the hand piece lies in securing adequate control of the volume of water supplied. This is particularly true when it' is desired to use an air-water spray or mist. In the systems of the prior art with which we are familiar because no means was provided for regulating the volume of water a proper air-water spray for most efiicient use could not be secured. When an air-water spray is desired, the water should be supplied in a very limited flow almost to the point where it constitutes a drizzle at the issuing nozzle which will be presently described. We have found that by using a metering valve 56 proper regulation of the volume of water may be secured so that when the air and water are properly mixed at the discharge thereof located in the hand piece a spray of air and water is delivered which for most purposes encountered in the practice of dentistry is' the proper form .of coolant. Asindicated diagrammatically, the metering valve 56 is of the needle type but this is optional as other forms of metering valves may be employed. Such metering valves including those of the needle type are well known in the art and need not be further described. i I One of the reasonswhy, in accordance with our understanding, shut off valves have been located for the most part on the hand piece in systems of-the type with which we are concerned is that it was thought necessary to locate the water shut ofi valve adjacent 'thcdischarge outlet. The purpose of this was to avoid a long conduit between the valve and the discharge outlet so that the device would not drip water when the hand piece shut off valve was closed. Dripping is notonly a source of annoyance to the dentist but also the water is likely to drip on a patients dress possibly resulting in damage thereto. We have found that by using solenoid shut off valves which close tightly and are rapid in their action, drip is minimized.

We have furtherfound that in t watersystem of our invention in which a pressure regulating valve and a metering valve are employed that the metering valve should be located on the down stream side of the pressure regulating valve. When the position of these valves is reversed, the pressure regulating valve acts as a resrvoir so that some drip will occur. We have found, when the needle valve 56 is located on the down stream side of the pressure regulator, the resistance introduced in-the line by the needle valve and the resistance of the relatively small diameter water tubing, coupled with the fact that when the solenoid valve is closed a vacuum is created on the down stream side of the solenoid valve tending to hold water in the tubing, that dripping of water is reduced to a minimum. This is particularly true since the use of a pressure regulating valve and a needle valve reduce the water stream to a relatively low-pressure, small-volume flow. At the low-pressure, small-volume flow We contemplate the resistance to fiow 'on the discharge side of solenoid valve substantially precluded dripping.

In Figs. 2 and 3, we have illustrated a hand piece equipped with a so called contra angle cutting unit and in Figs. 4 and 5 have shown a hand piece equipped-with a straight or in line cutting tool. It will be understood that these cutting tools may be selectively connected to the hand piece at 81 through a connection not shown. In Figs. 6 and 7 we have illustrated how the air-water unit mounted on the hand piece is disconnected from the block 36.

The block 36 receives the water and air conduits 26 and 27 respectively and has preferably metal tubes 82 and 83 extending thereto which the flexible conduits 26 and 27 areconnected.

Mounting block 36 has an angularly extending face for a purpose which will later appear. The air and water conduits 37 carried by the hand piece are flexible and are protected by a coiled spring 84 (Fig. I) wrapped around them which maintains them in a position such thatthey are not likely to be cut by the drive cord or belt and the dentist may extend his hand or fingers at least partway through the loop caused by the spring (see Fig. 1). The water and air conduits 37 numbered individually 86 and 87 which may be of rubber or flexible plastic material are connected to metal tubes carried in a plug 88 (Figs. 6 and 7) which may be of moulded rubber. The metal tubes are indicated by the numeral and have knurled or roughened portions, slightly enlarged, adapted to receive a flexible sleeve which may be slipped'partly over the knurled part to assist in holding the flexible tubes 86 and 87 on the tubes 90. The plug 88 has moulded therein tubular sockets which are adapted to receive the metal connecting tubes 82- and 83 so that the plug 88 may be disconnected from the metal tubes 82 and 83 and connected thereto as shown in Fig. 6.

Plug 88 has a boss 89 which carries a resiliently mounted bail 91. When the plug is applied to the metal tubes 82 and 83 the bail slides over the angularly extending face 80 so that the loop end of the bail is lodged over the lip of the mounting block 36 as shown in Fig. 6. The purpose of the bail is to insure that the water and air connections 86 and 87 will be connected to the water and air connections 82 and 83 respectively. This is not of major importance in the particular system shown herein but some manufacturers put out hand pieces requiring definite air and water connections.

Referring now to Fig. ,2 the handpiece generally indicated by the numeral 22 has the usual means 92 for .releasing and looking a cutting tool such as a burr 93 in a chuck located in the hand piece. A spring clip 93 of any suitable shape and form is provided which clips on over the hand piece and is held in position by the spring of the metal. A pair of nozzles, one for air and one for water such as nozzles 94 and 96 are soldered or otherwise secured as indicated at 97 to the spring clip. It would be possible to eliminate the clip and attach the nozzles directly to the hand piece. Each of the nozzles 94 and 96 has an internal longitudinally extending opening 98 which is slightly tapered inward from its open end and adapted to receive the correspondingly tapered end of a fitting 99. The fittings each have a through opening 101 and preferably are of metal with the opposite end of each somewhat enlarged at its outer diameter, as at 102, to receive the flexible tubes 86 and 187. The purpose of the outward taper. at the outer end .is to hold the flexible tubing more securely, after the tubing has been positioned. The fitting 99 has an enlarged part 103 which is knurled or otherwise roughened on its outer surface to receive a flexible sleeve 104 which may be shifted along the flexible tube 86 to overlap part of the knurling so as to hold the parts securely together.

Each of the nozzles 94 and 96 has a nozzle opening 106 which in the case of the contra angle hand piece extends outwardly and at an angle to the axis of the nozzle as illustrated in Fig. 2. In Fig. 3 the water nozzle opening has been indicated at 106 and the air nozzle opening at 107. Figs. 2 to inclusive are several times normal size but it will be apparent from an examination of the nozzle openings of Fig. 3 and the dotted extensions thereof through the walls of the nozzles that the openings are directed toward each other and that their axes cross at or adjacent to the burr 93.

It will be appreciated, since Figs. 2 and 3 are several times normal size, that the openings 106 and 107 are extremely small. Thus the water will issue from the nozzle 106 in an extremely fine stream which, when only water is to be applied to the drill and the tooth being drilled, is adequate for cooling and washing debris away from the cutting area. However, when the air is turned on the stream of water is sufficiently fine that due to the intersection of the streams of air and water the air stream breaks up the water stream into a fine air-water spray. The air stream picks up the water stream so rapidly that to some extent it appears to break it up into droplets adjacent the nozzle opening before dispersing it into a spray adapted to envelope the burr and the area being operated upon. The breaking up of the water into a fine air-spray provides maximum cooling effect for the amount of water supplied. In addition an important consideration is accomplished, namely, a reduction of the volume of water supplied to thereby minimize the necessity of the patient interrupting the dentist to clear his mouth of water.

In Figs. 4 and 5 we have illustrated a straight or in-line hand piece which has a spring clip 108 and water and air nozzles 109 and 110 respectively. The nozzle openings 111 are in-line with the axes of the nozzles, as will be apparent from an examination of Fig. 5 but the nozzles are mounted so that their axes, extended, cross at 112 at or adjacent the burr for the purposes previously described in connection with the contra angle mounting of the nozzzles.

It will be understood that in the normal use of the device that in changing from a contra angle to an in-line hand piece, it is merely necessary to remove the contra angle hand piece and slip the nozzles 94 and 96 ofi the ends of the fittings 99. Then the in-line drilling unit of Figs. 4 and 5 together with its nozzles 109 and 110 maybe substituted for the contra angle, slipping the fittings into the openings in the ends of the nozzles 109 and 110. If desired and the dentist finds it more convenient, the conduits may be disconnected by disconnecting the plug 88 from the mounting block 36. In such case a flexible conduit up to and including the plug 88 will be maintained assembled on both the contra angle and the straight or in-line hand piece.

While we have shown and described the preferred form of our invention it will be apparent that various modifications and changes may be made therein particularly in the form and relation of parts without departing from the spirit of our invention as set forth in the appended claims.

I claim:

1. Dental apparatus wherein a tooth cutting tool is actuated by motor means at high speed, comprising, in combination, an air conduit for conducting air under pressure from a source of supply, a water conduit having a pressure controller therein for conducting water under pressure from a source of supply, means for mixing the air and water, means for controlling the flow of air and water comprising a solenoid valve in each of said conduits, switch means for selectively controlling said solenoids, start and stop means for said motor means and means for supplying air, water or a mixture of air and water to said cutting tool depending upon the position of said switch means when said start and stop means is actuated to start the motor means. I

2. Dental apparatus in accordance with claim 1 wherein the water conduit has a metering valve operable therein.

3. Dental apparatus in accordance with claim 1 wherein said pressure controller is between the source of supply and the solenoid valve and a metering valve is provided between the pressure controller and the mixing means.

4. Dental apparatus wherein a tooth cutting tool is actuated by motor means at high speed, comprising, in combination, a hand piece, an air conduit for conducting air under pressure from a source of supply to said hand piece, a water conduitfor conducting water under pressure from a source of supply to said hand piece, a water nozzle mounted on said hand piece, an air nozzle mounted on said hand piece, said air and water nozzzles being directed angularly with respect to each other whereby the issuing streams cross adjacent said cutting tool, said water conduit having metering means therein between the source of supply and said handpiece enabling the supply of water to said water nozzle to be reduced in volume to an extent such that the air stream will break up the water stream into a fine mist.

5. Dental apparatus in accordance with claim 4 wherein meanslare provided for controlling the flow of water through said water conduit, said means including a solenoid actuatedvalve, a pressure controller between the source of supply and the solenoid actuated valve and a metering valve between the pressure control valve and the water nozzle.

Y 6. Dental apparatus wherein a tooth cutting tool is actuated by motor means at high speed comprising, in combination, a hand piece for carrying and directing said cutting tool, a water conduit for conducting water under pressure from a source of supply to said hand piece, means for controlling the flow of water through said conduit comprising a solenoid actuated shutolf valve, a pressure controller between saidsource of supply and the shutoff valve and a metering valve between said pressure controller and the hand piece.

7. Dental apparatus wherein a tooth cutting tool is actuated by motor means at high speed comprising, in combination, a hand piece for carrying and directing said cutting tool, an air conduit for conducting air under pressure to said hand piece, a water conduit for conducting water under pressure to said hand piece, a solenoid valve in said air conduit between a source of air under pressure and said hand piece for opening and closing the air conduit to the How of air, a solenoid valve in said water conduit between a source of water under pressure and said hand piece for opening and closing the water conduit to the flow of water, a pressure controller in said water conduit between the source of water under pressure and said water solenoid valve, a metering valve in said water conduit between the water solenoid valve and said hand piece and circuit means including a foot actuated switch and said solenoids for controlling the flow of air and water to said hand piece.

8. Dental apparatus in accordance with claim 7 where in portions of both said air and water conduits are flexible and means are provided for detachably attaching said flexible portions to said hand piece.

9. Dental apparatus wherein a tooth cutting tool is actuated by motor means at high speed comprising, in combination, a hand piece for carrying and directing said cutting tool, an air conduit for conducting air under pressure from a source of supply to said hand piece, a water conduit for conducting water under pressure from a source of supply to said hand piece, said hand piece carrying an air nozzle and a water nozzle to which said conduits are connected, said nozzles being directed at an angle to each other so that the projected streams cross each other adjacent said cutting tool and said water conduit including controllable means for metering the flow of water to a trickle whereby said air stream will break up said water flow into a mist, and means including an electrical circuit for controlling the flow of air and water through said conduits, means in said circuit for controlling the starting and stopping of said motor means, a solenoid actuated shutoff valve in each of said conduits the solenoids of which are included in said circuit, switch means in said circuit for controlling said solenoid valves, said switch means enabling the selection of a flow of air, a flow of water, or a flow of a mixture of air and water to said hand piece whenever said motor means controlling means is actuated.

References Cited in the file of this patent UNITED STATES PATENTS 1,000,785 Cunningham Aug. 15, 1911 1,648,273 Hofschneider Nov. 8, 1927 2,098,732 Prather Nov. 9, 1937 2,532,054 Broussard et a1 Nov. 28, 1950 2,557,377 Ganz June 19, 1951 

